Chevy Big-Block Engine - Big Time Power

When It Comes to Big-Blocks, What's the Price for Power and Are Strokers Worth It?

Here's the scenario: You're looking to make big power, so you're looking to build a big-block. Sure, you can make plenty of ponies with a small-block, but it's hard to match the brute force provided by sheer cubic inches. When the first "Mystery Motor"-powered Chevrolet won the 1963 Daytona 500, an undeniable big-block mystique was created. More than 40 years later, that aura of all-out performance is as strong as ever. So you want a big-block. You know how much money you have, and you want to get as much performance as possible for your dough. What are your options? Is the 454 still a viable performer, or is bigger--as in 496 or 540--always better?

Size MattersThat's the question we first set out to answer: 454 versus 496 versus 540? We planned to look at the power potential and price of this trio. Our exploration of the big-block world, however, quickly led us in a slightly different direction. There are plenty of 454-powered vehicles still making the scene, but they're becoming the exception rather than the rule when it comes to performance builds. Stroker rotating assemblies, we learned, cost nearly the same as a stock setup, making them more cost effective. If it costs the same to build a 496 or a 506, then why not do it and make more power while you're at it?

The "bigger is better" ethos doesn't stop there. For many builders, especially those beginning from scratch, the increasingly affordable price of aftermarket blocks makes 540 ci the displacement starting point. "People want the biggest and baddest engine they can get," we were told, and whether they buy it all at once in crate form or in pieces over time, that's what the aftermarket is giving them. Whereas 500 hp was once a respectable number, 600 seems to be the new minimum.

Mathematical GymnasticsIn fairly simple mathematical terms, the quest for more displacement is logical. More displacement means more power, but you knew that, right? In general, a properly tuned production automotive engine produces 1.0-1.5 hp per cubic inch. Where a particular engine falls depends on many factors, so we'll use 1.3 hp per cubic inch as a middle figure. That means a 454 can support almost 600 hp (454 x 1.3 = 590.2). Indeed, many do. Using the same multiplier, a 496 can support 645 hp. And remember, the price difference between the two is minute. We're sure you see where this is heading. So we ask, how much does it cost to build a 454 that can support 600 hp, as opposed to the cost of a 540, which can support more that 700 hp?

Exploring the Big CountryBy way of examining this issue, we set out to take a big-block cross section of sorts. We talked to a number of engine builders and parts suppliers, and we pretty much asked the same questions: What's your best bang-for-the-buck package? What are people actually buying? And, perhaps most importantly, we asked our industry sources for the bottom line, in other words, "What is the price of power?"

Of course, we also wanted to get an idea of what kind of power various big-blocks actually make, so we rifled the dyno-pull files at Westech for a few examples. It may not be exactly scientific, but it is grist for the mill. Let the bench racing begin.

HEADS UPIf we learned anything from our Rat-motor reconnaissance, it's that big-block Chevy heads ain't cheap. Some may cost only a few hundred dollars more (apiece) than their small-block counterparts, but many cost half as much again--or more. Anecdotal testimony came from our expert sources, almost all of whom sell plenty of short-blocks to customers who already have cylinder heads. With this in mind, we sought the voice--or rather voices--of experience, namely our friend Steve Brul of Westech Performance and our new friend, Harold Bettis of SuperFlow Technologies. Here's what our experts had to say.

CHP: All right, guys, what's your take on the oval-port versus rectangular port deal?Steve Brul: The current thinking is that the oval shape is better than a rectangular port, as shown in current Pro Stock technology. Harold Bettis: An oval-port head leaves fewer opportunities for eddies and irregularities of flow in the corners, because there are no corners.

CHP: So oval ports are better? SB: Generally, with traditional-style oval-and rectangular-port heads, the smallest port with the highest flow volume is best. HB: Yes, proper flow numbers are more important than size. Think of the air as a concentration of energy. If that concentration is high, it's easier to get air into the cylinders and harder to get it out (reversion).

CHP: So how does that relate to port shape?SB: You should refer to oval and rectangular ports as a function of size, not of shape. HB: At power levels over 550 hp, a rectangular port is the normal trend. When the volume changes to meet this level, it's easier to get the needed flow from a rectangular-port head. SB:HB: Remember, an engine does most of its work and spends most of its time at part throttle, and it needs to be happy there. Higher average power, under the curve, is what makes it go down the road. And the guy who gets on the torque curve first wins.

CHP: Do people tend to use heads that are too large?HB: People build engines to make max power, then drive them at part throttle. Force is not the issue; air speed is. Given that, it's better to be slightly small (when it comes to port size) as opposed to slightly large.

CHP: So, is there any kind of formula for determining what size head to use?SB: The better head is dependent on application, rpm range, and size. Obviously, a 7,000-rpm 572 isn't going to want the same head as a 5,500-rpm 454. Sizing a cylinder head comes down to a lot of previous data. That being said, a reasonable power potential on a high-quality street engine is 2 hp per cfm. HB: If you measure the intake flow of the complete air tract, with restrictions, and multiply that number by 0.26, you'll get a number that represents power per cylinder. So 400 cfm times 0.26 equals 104, which times 8 cylinders equals 832 hp.

CHP: Any parting words?HB: The way to go about creating an engine is to determine the goals and objectives, make a plan, and set a budget. If one gets out of kilter, then you have to readjust.

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GM Performance Products' ZZ572/ 620 Deluxe crate engine is one of the General's best-sellers. This 9.6:1, 4.560x4.37-inch hydraulic-roller motor is based on a Gen VI tall-deck block with a machined fuel-pump boss. (Not all Gen VI blocks have this provision.) A turnkey version retails for $12,786 through Scoggin-Dickey parts center; you're lookin' at $8,000 even for a short-block.

The ZL1 has been synonymous with big- block exotica since it was introduced in '69 Corvettes and Camaros, and it's still a highly coveted piece. The new-and-improved version has four-bolt splayed main caps and screw-in freeze plugs. It only weighs 110 pounds, but its price--$4,690--is somewhat heftier.

Speed-O-Motive sells this 454-based 506ci big-block for $7,250. Power checks in at about 575 hp, making this one a good bang-for-the-buck deal. Wanna spend more? Factory 454 and 502 blocks support 800-plus horsepower. Aftermarket blocks like the Dart and Merlin can support double that or even more when power adders are used.

Although you can't see them here, AFR's Tony Mamo recommends the company's as-cast heads with the optional CNC bowl-blend. "The ports are still effective," he tells us, "but the CNC work is the same as in a full port job, which gives more low- and medium-lift flow." The chamber work costs $300 extra, but the gain is about 30 hp--quite a deal. A pair of 305cc heads with the bowl work go for $2485.

Smeding Performance's most popular big-block is its 540 Extreme. This hydraulic-roller motor is based on a standard-deck Gen VI block and runs 10:1 compression with the aforementioned AFR 305cc heads. Eleven grand gets you 680 lb-ft of torque to go with the engine's 620 hp.

Dart's Jack McInnis says that the Pro 1 BBC heads are its best-sellers, "largely because people want aluminum heads." This 275cc oval-port is the newest member of the family, created for big-blocks that don't need a mondo head. Count on paying about $1,200-$1,400 apiece for Pro 1 heads.

Once something of a rarity, Dart's Big M blocks are now commonly used as the basis for big-inch big-block builds. The scalloped water jackets, priority main oiling, and overall beefy construction are all advantages. Standard-deck, 4.500-inch-bore versions start as low as $2,200.

Shawn Mendenhall of Probe Industries gave us a quick education on big-block pistons. The FPS flat-top slug uses stock rings and a press-fit pin and has a stock compression height. The SRS mid-dome version can be used with open- or closed-chamber heads and has a 1.270 compression height. Compression would be about 10:1 with an 119cc head. The SRS high-dome piston is for open-chamber heads only; compression would be about 14:1. Prices start at about $435 for a set of flat-top pistons; figure on another $65 for rings.

Big-block rods come in a variety of lengths, most of which are pictured here. There's also a 6.250-inch rod, which Probe uses in several of its 460 and 489 big-block builds.1. This 6.135-inch is Probe's 5140 forged replacement for a stock-sized rod. At $180 per set, it's an affordable step up.2. Rods measuring 6.385 inches are used in many big-blocks, especially the popular 540s.3. This 6.535-inch 4340 H-beam rod is 0.400 inch longer than stock, so it requires a piston with a 0.400-inch-shorter compression height, or a tall-deck block.4-5.A 6.700-inch rod is usually only found in a tall-deck motor; the 6.800-inch arm requires it.

The forged crank up front has a 4.250-inch stroke, while the cast piece behind it runs a stock 4.00-inch stroke. Note the sharper knife-edging on the forged crank's throws. Although the strength of a forged crank can't be denied, a cast crank in a properly prepped engine can handle 700-800 hp.

Later engines, such as GM's Gen V and VI big-blocks, use a one-piece rear crank seal (left). The earlier Mark IV versions and its aftermarket offspring utilize a traditional two-piece setup (right).

Q&A With Jack Mcinnis of DartT MachineryCHP: What's the going rate for a Big M block these days?Jack McInnis: It's around $2,200-$2,300 for a standard-deck-height Sportsman, and $2,600-$2,700 for the Comp version. The main difference is that the Sportsman has ductile iron main caps.

CHP: How do those prices stack up against the competition?JM: We try to have a fair price, but we don't merely try to meet the bottom line. We prefer to have a quality product.

CHP: That being said, are the Big M blocks selling well?JM: Yeah, they are, absolutely. We're doing a good business in those blocks.

CHP: What's your take on that?JM: By the time someone finds a core, has it inspected, and has the machine work done, they're close to the price of one of our blocks. When you buy one of ours, it's virtually ready to go.

CHP: What are the other reasons to go with a Big M block?JM: Once somebody makes the move to a good aftermarket block, they won't go back. The thicker cylinder walls have many more rebuilds in them--or room for more displacement. With a good 454, you can go 0.060 or 0.080 over. You can go almost 0.400 over with ours, or just get it with a 4.600-inch bore.

CHP: What are the other advantages of the Dart block?JM: For one, the block webs are much thicker and stronger. The scalloped water jackets improve cooling, and the "true" priority main oiling system makes sure the main bearings always have enough lubrication. These blocks are also made from a much harder, denser alloy than a stock block. Someone would have to spend a lot on a stock block to get even close. The value someone gets with a Dart block is tremendous.

CHP: Dart is also in the cylinder head business. What's you best-seller in that department?JM: That would be our Pro 1 aluminum heads. They go for $1,200-$1,400 apiece. Most of the standard GM stuff came as rectangular, so we accommodate that. We created our new 275cc oval-port head to fill that niche. It'll be good for 454- or 468ci hot street motors. The port size increases air velocity, and therefore performance.

CHP: What's the most common mistake you see when it comes to choosing big-block heads?JM: Everyone thinks bigger is better, but it depends on what you use the thing for. If it's a street car that goes to the strip every once in a while, it'll be happier with a smaller head.

Q&A With Jim Escamilla Of Larry's PerformanceCHP: What's your most popular big-block?Jim Escamilla: Our best-seller is our 454 four-bolt main short-block. It goes for $1,995 with forged flat-top pistons. It would come in at 9:1 or 9.5:1 compression with small-chamber heads.

CHP: Do you mostly sell short-blocks?JE: Ninety-five percent of our big-block sales are short-blocks. Some guys might buy a set of aluminum heads, but I find that most hot rodders already have a set they want to use.

CHP: What type of cam do you put in most of them?JE: Ninety percent go out with hydraulic flat-tappet cams. Most guys we sell to just want a solid motor.

CHP: How about crate motors? JE: We do have our 496 Track Pro package. It comes with a Scat cast crank, SRP forged pistons, and GM Track Pro oval-port heads. We rate it at 496 hp and 550 lb-ft of torque, and it sells for $5,550.

CHP: Do you get much call for anything more radical? JE: Yes. We're currently working on a 14:1 forged dome-piston motor. The customer wants it for a local annual race event called the Hangover Nationals. We can do stuff like that, but how many people can afford to buy it?

CHP: What's it based on?BS: We use a Gen VI 502 block with a 4.500-inch bore and 4.250-inch stroke. It comes with a hydraulic-roller cam. Maybe one out of 10 ask for a solid roller. We used to do a 454, but it pretty much cost the same as the 540.

CHP: What other big-blocks does Smeding build?BS: The 565 Extreme and the Blown 540 are our other regular builds. The 565 uses a standard-deck Dart block and CNC-ported heads. It makes 690 hp and goes for $12,995.

CHP: How would you characterize these two engines?BS: The 540 is more of a cruiser engine, while the 565 is more for street-strip duty. It seems to be for the younger guy who wants to flex his muscles more.

Q&A With Scott Shafiroff Of Shafiroff Racing EnginesCHP: You build a lot of different big-blocks. Which one packs the most bang for the buck?Scott Shafiroff: That would be our UltraStreet 540/695hp Classic. It goes for $8,995. And it can be upgraded to more than 700 hp by switching to the Dart Pro 1 CNC heads. So for less than $9,500 you can get 725 hp.

CHP: What trends are you seeing in the big-blocks people are buying?SS: Hydraulic-roller cams are very popular, though I say the good ol' solid roller is still best.

CHP: What else have you noticed among those who build big-blocks? SS: The biggest problem with horsepower per dollar is that people immediately think about a bigger cam and heads, but no one wants to spend money on the short-block. Everything has to be in balance. That's what a good engine shop does for a guy.

CHP: Are there options besides buying a complete engine?SS: We sell a 540 short-block with the cam degreed in. People don't have 10 grand, but they may have five and a set of heads they want to fit on. A lot of people like to put it together themselves. We also sell a lot of short-blocks along with heads for the same reason.

CHP: Are there any advantages to that approach?SS: We know our combo works, and it's kind of nice to know it's a guaranteed deal. It's like buying one of our engines over time. And people make mistakes every day while trying to homebrew.

CHP: For instance?SS: The mild motors, when properly put together, can actually run lower compression and still make more power, because the parts are happier.

CHP: You also mentioned your 582/745 hp Big Dawg engine. SS: The 582 is a tremendous motor. It's for guys who want maximum power but can't fit a tall-deck motor under their hood. That's what they want; it has to fit under the hood.

CHP: Does it sell well?SS: Yes, but the 540 short-block outsells it five to one. A set of 396 oval-port heads will bolt right on, and it's physically the same size as a 396. It looks like a regular motor. That's the sleeper...the hot ticket.

CHP: You use a lot of different engine blocks. How do you decide which one to start with?SS: The Gen VI is perfectly acceptable for all 540s. If they're using a power adder, people are better off getting a Merlin block.

CHP: What about some of the aluminum blocks you employ, such as the Donovan?SS: Well, it saves weight and runs cooler, and they're much easier to repair, which is good for racing engines. But in a street car, it's just a cool thing to have.

Q&A With George Ullrich From Speed-O-MotiveCHP: Which of Speed-O-Motive's big-blocks packs the most bang for the buck?George Ullrich: I'd have to say our 506 Budget Stroker Engine. It's a 0.100-over 454, so it has a 4.350-inch bore and a 4.250-stroke. We use a 6.385-inch rod.

CHP: What kind of heads and cam do you use? GU: We use Dart Iron Eagle BBC heads, and most people go for a hydraulic flat-tappet cam.

CHP: OK, what kind of power does it make, and what does it cost?GU: Our 506s usually make 550-575 hp. A full engine costs about $7,250, turnkey and dyno-tuned.

CHP: Which engine in your best-seller?GU: Our 540 would be right up there. The Street Master version runs 10.5:1 compression and makes about 700 hp. We use RHS iron heads, with aluminum heads available as an upgrade. It goes for about $10,600.

CHP: You use a Dart block for that engine?GU: Yes, and all forged internals. It's very heavy-duty.

CHP: Could you make the same amount of power based on a 454 block? GU: We could bump one up to about 650 hp, but by the time you put on aluminum heads and a roller cam to get there, the cost would be up to about 10 grand.

CHP: So that engine would cost almost as much as one of your Dart-based 540s? GU: Yes, but without the advantages of the Dart block. The cooling is better, and the priority main oil system makes for a more stable platform.

Q&A With Bill Mitchell Of World ProductsCHP: Bill, what's hot at World Products?Bill Mitchell: I'd say the 572 Hardcore version big-block. Hardcore signifies a 4500-series carb, single-plane manifold, and it runs a solid-roller cam. It's very popular, but at $12,495 it's not cheap.

CHP: What kind of power are we talkin' here?BM: The iron-head version makes 675 hp; with aluminum heads it makes 20 more.

CHP: Are there any other engines that are doing well? BM: The 540 Hardcore big-block is among our top 10 most popular products. It comes with cast-iron or aluminum heads and makes 610 or 630 hp. It goes for about $11,000.

CHP: We understand you've just done some cam testing on that motor?BM: Yes. With a hydraulic cam and lifter swap, the 540 jumped up to 690 hp, along with 618 lb-ft of torque. That's 60 extra horsepower for $600. We anticipate that the hydraulic-roller cam will be a big sell- ing point.

CHP: World Products is well known for its aftermarket blocks. What are the advantages of going to a Merlin block?BM: The key to making power is displacement. When you've got the architecture to build a big motor, it makes sense to use it.

Q&A With Jamie Meyer Of GM Performance PartsCHP: So, does GMPP still actually sell any 454s?Jamie Meyer: Well, it would obviously be our most affordable big-block. And we sell a lot of our serpentine accessory beltdrive setups for them.

CHP: Then what's the engine people are going for? JM: We can't keep the 572s in stock. People want the biggest, baddest thing they can get. The Ram Jet 502 also does well because its sort of trick looking. It comes as a surprise when you pop the hood. Our partial engines are also popular, since a lot of people have their own cylinder heads.

CHP: Any partial engine in particular?JM: The 502 short-block. It's a sleeper. There are generations of guys out there with 454s who are replacing their short-blocks with a 502. It looks like a 454, but then, Surprise!

CHP: What else is popular?JM: Many people are buying their engines in kit form. They save money, all the parts go together, and they can personalize their engines.

CHP: OK, back to the 572s. There are two versions: the 620hp pump-gas version, and the 12:1-compression, 720hp version. What's the sales breakdown like?JM: It's just about 50/50, which surprised us. The 572/720 was intended for bracket racers, but we're seeing some extreme street cars, and they'll use that version.

CHP: Is there any other GMPP big-block we should mention?JM: The ZL-1. It is the most coveted block out there, in my mind. We do sell them, and they're very expensive.

CHP: It seems that it's worth GM's while to keep making big-blocks. JM: The bottom line is that a big-block is a very American piece of history. They deliver on the promise of a musclecar...they make you feel alive.